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I <br />' 16 December 2004 <br /> • AGE-NC Protect No 97-0249 <br />' Page 7 of 8 <br /> - The most intense TPH-d-impacted ground water was reported from Hydrologic Unit 1 in the <br />' area of well MW-3 at a concentration of 1,700 µg/1 (Figure 10), an isolated TPH-d <br /> occurrence was reported at Flag City Chevron well MW-12A, approximately 200 feet <br />' southeast of the site <br /> The most intense on-site MTBE-impacted ground water was reported from Hydrologic <br /> Unit 1 in the area of Three B's Truck Plaza well MW-8A at a concentration of 110 µg/1 and <br />' from Flag City Chevron well MW-16 at a concentration of 43 µg/1 Other on-site MTBE <br /> detections were from Hydrologic Unit 2 in the area of Flag City Chevron well MW-17 at a <br /> concentration of 40 µg/1 (Figure 12) and from Hydrologic Unit 3 in the area of Flag City <br /> Chevron wells MW-11B and MW-18 at concentrations as high as 130 gg/1 (Appendix A) <br /> On-site MTBE-impacted ground water from Hydrologic Units 1 and 2 are depicted on <br />' Figures 11 and 12, respectively <br /> - The highest off-site concentrations of dissolved MTBE were detected in monitoring wells <br /> toward the east and northeast, in water samples collected from Flag City Chevron wells <br />' MW-8A(220 gg/l, Hydrologic Unit 2), and MW-19A(1,300 gg/l,Hydrologic Unit 1) Off- <br /> site MTBE-impacted ground water from Hydrologic Units 1 and 2 are depicted on Figures <br /> 11 and 12, respectively <br /> G Low concentrations of TBA and 1,2-DCA have been detected from wells MW-1, MW-2, <br /> MW-3, MW-5, MW-6, MW-8A, MW-10A and MW-11A, suggesting that only a minor <br />' TBA-impact and 1,2-DCA-impact to ground waterm Hydrologic Unit 1 is present at the site <br /> O The lateral and vertical extent of the dissolved petroleum hydrocarbon plume is not known <br />' toward the northeast of Three B's Truck Plaza well MW-2, toward the south of Three B's <br /> Truck Plaza well MW-6 and toward the south of Flag City Chevron wells MW-16/17/18 <br /> (Figures 9, 10, 11 and 12) <br /> 5.0. RECOMMENDATIONS <br /> Based upon the results of the third quarter 2004 investigation, AGE recommends <br /> p q g <br />' - Continued quarterly ground water monitoring of wells MW-1 through MW-12, the next <br /> quarterly ground water monitoring event is tentatively scheduled for 28 and 29 December <br /> 1 2004, <br /> Continue to conduct future ground water monitoring events concurrently with the Flag City <br /> Chevron site (6421 Capitol Avenue), <br />' Advanced GeoEnvironmental,Inc <br /> 1 <br />